The present invention relates to methods of making microelectronic assemblies such as semiconductor chip packages.
Modern electronic devices utilize semiconductor chips, commonly referred to as xe2x80x9cintegrated circuitsxe2x80x9d which incorporate numerous electronic elements. These chips are mounted on substrates that physically support the chips and electrically interconnect each chip with other elements of a circuit. The substrate may be a part of a chip package including a single chip and equipped with terminals for interconnecting the chip with external circuit elements. The interconnection between the chip and its supporting substrate is commonly referred to as a xe2x80x9cfirst levelxe2x80x9d interconnection. The interconnection between the substrate and the larger elements of the circuit is commonly referred to as a xe2x80x9csecond levelxe2x80x9d interconnection.
In a wire bonding process, the substrate has a top surface with a plurality of electrically conductive contact pads disposed on the top surface near the periphery of the substrate. The chip is secured to the top surface of the substrate so that the contact pads on the substrate lie outwardly of the chip. The chip is mounted with the back surface of the chip confronting the top surface of the substrate and with the front surface of the chip facing upwardly, away from the substrate, so that electrical contacts on the front surface are exposed. Fine wires are connected between the contacts on the front face of the chip and the contact pads on the top surface of the substrate.
Semiconductor chip assemblies may also utilize a component having bond windows for making electrical connections between terminals on the component and contacts on a semiconductor chip. Such a component is disclosed in certain embodiments of WO 94/03036, the disclosure of which is hereby incorporated by reference herein. The component comprises a layer having a gap and leads extending across the gap so that the leads are supported at both ends. The component is disposed on top of a semiconductor chip so that the leads generally extend over the contacts of the chip. A bonding tool is utilized to bond each lead to a contact on the chip, by advancing the tool toward a lead and forcing the lead toward the contact on the chip. The lead may include a frangible section that breaks when the lead is forced toward the contact. Heat and/or ultrasonic vibration is applied to the lead by the tool so as to bond the lead to the contact. Prior to bonding to a semiconductor chip, the leads are secured to the component and somewhat protected during handling of the component and arranging of the component with the semiconductor chip. However, a bonding window is required to provide access to the contacts.
Despite the foregoing improvements, further advancement in making microelectronic assemblies is desirable.
The present invention addresses these needs.
In one aspect of the present invention, a method of making a microelectronic assembly comprises connecting a first end of a lead to a contact on a microelectronic element. A second end of the lead is connected to a stage disposed adjacent to the microelectronic element. The microelectronic element is juxtaposed with a microelectronic component having terminal pads exposed at a first side of the microelectronic component. The lead is disconnected from the stage, either before or after juxtaposing the microelectronic element with the microelectronic component. The lead is bonded to one of the terminal pads on the microelectronic component.
Methods in accordance with embodiments of the invention interconnect a microelectronic element with a microelectronic component without the use of a bond window for accessing the leads. In addition, the leads may remain bonded to the stage during some or all of the handling of the microelectronic element and are thus supported during handling, making damage to the leads less likely. Components having bond windows must have bond windows aligned with the contacts on the microelectronic element to be assembled with the component. In a method in accordance with embodiments of the invention, microelectronic elements of different sizes and having contacts in different locations may be accommodated.
In preferred embodiments, the lead comprises a wire formed by wire bonding a first end of the wire to the contact on the microelectronic element, extending the wire past a peripheral edge of the microelectronic element, and bonding a second end of the wire to the stage. The microelectronic element is preferably mounted to the stage and juxtaposed with the microelectronic component by moving the stage to the microelectronic component. The microelectronic element preferably has a first surface and a second surface facing oppositely from the first surface and the contacts are exposed at the first surface. The microelectronic element is preferably juxtaposed with the microelectronic component so that the first surface faces the first side of the microelectronic component, so that the contacts on the microelectronic element face the terminals on the microelectronic component.
In embodiments having the wires bonded to the stage while the microelectronic element is juxtaposed with the microelectronic component, the wires are supported during handling and arranging the microelectronic element with the microelectronic component. When the microelectronic element is juxtaposed with the component so that the contacts on the microelectronic element face the component, the wires may be shorter than in other embodiments and performance of the completed assembly is enhanced.
In other embodiments, the microelectronic element is juxtaposed with the microelectronic component so that the second surface of the microelectronic element faces the first side of the microelectronic component. In this embodiment, the contacts on the microelectronic component face away from the component.
The microelectronic element is preferably assembled with the microelectronic component. At least one pad element is preferably assembled with the microelectronic element and the microelectronic component so that the at least one pad element is disposed between the microelectronic element and the microelectronic component. The at least one pad element may comprise a compliant pad element.
The microelectronic element may comprise at least one semiconductor chip, a temporary support layer, a sacrificial layer, a connection component, a printed circuit board, a wafer or tape of semiconductor chips, or a substrate. The microelectronic component may comprise a semiconductor chip, a printed circuit board, temporary support layer, a sacrificial layer, a connection component, a substrate, or a wafer or tape of semiconductor chips, and may incorporate a variety of conductive features on surfaces thereof or incorporated within the component.
Methods in accordance with embodiments of the present invention may comprise making the microelectronic component by forming the terminal pads on a first side of a dielectric layer, forming conductive traces on the first side, and forming connection terminals on a second side of the dielectric layer so that the terminal pads are electrically connected to the connection terminals by the conductive traces. Solder may be applied at the second side of the dielectric layer to form the connection terminals.
The lead is preferably disconnected from the stage by severing a portion of the lead connected to the contact from another portion of the lead connected to the stage. The bonding of the lead to the terminal pad may include displacing the lead in a direction toward the terminal pad utilizing a bond tool.
The lead, in other preferred embodiments, is releasably connected to the stage and disconnected from the stage by removing the microelectronic element from the stage. For example, the lead may be connected to an upper surface of the stage and the upper surface may comprises a non-stick surface.
In certain preferred embodiments, the stage has a first surface and includes a conduit being open on the first surface. The second end of the lead is bonded to the first surface so that the lead extends over the conduit. The lead may be disconnected by inserting a cutting tool into the conduit and severing a portion of the lead connected to the contact from another portion of the lead connected to the stage. The lead is preferably bonded to the terminal pad by inserting a bonding tool into the conduit, displacing the lead in a direction toward the terminal pad and bonding the lead to the terminal pad.
In another aspect of the present invention, a method of making a microelectronic assembly comprises connecting a first end of a wire to a contact on a microelectronic element having peripheral edges. The wire is extended beyond the peripheral edges of the microelectronic element. A second end of the wire is bonded to a stage disposed adjacent to the microelectronic element. The microelectronic element is assembled with a microelectronic component having a first side and a second side. The microelectronic component has terminal pads exposed at the first side and connection terminals exposed at the second side. Each connection terminal is electrically connected to one of the terminal pads. The wire is disconnected from the stage, either before or after the assembling. The wire is bonded to one of the terminal pads.
At least one pad element is preferably assembled with the microelectronic element and the microelectronic component so that the at least one pad element is disposed between the microelectronic element and the microelectronic component. The at least one pad element preferably comprises a compliant pad element.
The microelectronic element may comprise at least one semiconductor chip.
The wire is preferably disconnected from the stage by severing a portion of the wire connected to the contact from another portion of the wire connected to the stage.
In certain preferred embodiments, the stage has a first surface and includes a conduit open on the first surface. The second end of the wire is bonded to the first surface so that the wire extends over the conduit. The wire is bonded to the terminal pad by inserting a bonding tool into the conduit, displacing the wire in a direction toward the terminal pad and bonding the wire to the terminal pad.
Preferably, the microelectronic element is mounted to the stage and the microelectronic element is juxtaposed with the microelectronic component by moving the stage to the microelectronic component.
In a further aspect of the present invention, a stage for making a microelectronic assembly comprises a base arranged to hold a microelectronic element during positioning of the microelectronic element with respect to a microelectronic component. The stage has walls extending upwardly from the base and terminating in an upper surface. The walls define a conduit that is open at the upper surface. A bonding tool is arranged to be introduced toward a lead extending across the conduit at the upper surface and to apply energy in bonding the lead to a pad on a microelectronic component.
The base of the stage may define vacuum holes for holding the microelectronic element. In another alternative, the stage has a clamp for holding the microelectronic element.
The stage may include a cutting tool for separating from the stage a lead bonded to the upper surface. The cutting tool is preferably arranged to be introduced toward the lead through the conduit.